The invention relates to a device for cleaning gases, in particular air, with an electrostatic filter unit inside a tube-shaped covering, which has an intake opening at one end and an outlet opening at the other end for a gas flow or airflow to be cleaned. The device is installed inside a housing with an air intake opening and an air outlet opening and an essentially airtight, closed surface shell.
As a result of the increasing forward push in environmental consciousness in recent years, progressively higher requirements must be met with respect to clean air as well maintaining the clean air. Meeting the increasingly stricter legal limits for contaminating the air we breathe with all types of pollutants has become a major challenge. In view of this, considerable efforts are made, in particular in the industrial sector, to meet the legal limits for air pollution values.
Different types of air cleaning devices are known, in which different operational principles are realized. Particularly good results are obtained with an air cleaner having an electrostatic filter unit, as described for example in the German reference DE 195 30 785 C1. The filter unit for this air cleaner comprises a gas ionizer and, following in flow direction, a tube-shaped electrostatic precipitator. The gas ionizer consists of an outer tube made of metal and a cylindrical insulating body on the inside, which supports a metallic ribbon spiral with the tips arranged tightly side-by-side. The precipitator consists of outer and inner tubes that are arranged concentric to each other. A high-voltage field is generated and maintained between the outer tube for the ionizer and the metallic ribbon spiral, as well as between the outer tube and the inner tube of the precipitator, which initially ionizes the particles in the air and then precipitates these on the tubes of the precipitator. A filter unit of this type is described in German reference DE 39 30 872 C2, to which we also point for additional details. The air cleaners containing these electrostatic filter units, which are known from German reference DE 195 30 785 C1, permit only a limited flow-through of air. They are designed as stand-alone devices and above all can be used for cleaning the room air in living rooms, restaurants, offices and smaller business spaces. Since their capacity for technical reasons cannot be increased easily, they are hardly suitable for use in the industry. Thus, the filtering and air cleaning devices used in the ventilation and air exhaust systems in the industry for factory buildings and production areas are based on the principle of mechanical filtering, and/or electrostatic precipitators with horizontal plate arrangements. These air cleaners require a high expenditure to achieve a sufficiently high cleaning effect.
Reference EP 0 352 451 A2 discloses an electro-filter for solid materials in gases, for which a gas to be cleaned is guided through pipes in which foreign-body particles are electrostatically precipitated out. The pipes are welded together solidly and form a rigid, self-contained spatial unit.
U. S. Reference U.S. Pat. No. 4,042,354 A describes an electrostatic gas-cleaning device, for which electrode-forming pipes are installed inside a housing in support plates, thereby also forming a rigid, self-contained spatial unit.
Thus, it is the object of the invention is to provide an additional air cleaner of the aforementioned type, which is particularly suited for use in the industry and which makes it possible to meet with minimum expenditure the strict limit values specified for the pollution levels in the air.
This object is solved according to the invention in that several or all filter units, extending parallel to each other, which are combined to form an assembly that is adapted to the inside space of the housing and can be installed into or removed from the housing as a unit. Further developments, useful modifications and advantageous embodiments of the device according to the invention are described herein.
In many application cases, particularly if the device is designed to be free standing, the filter units can be inserted from one end of the housing into the holders provided inside the housing. In particular with larger air-cleaning systems according to the invention or with devices installed into the air ducts for air conditioning or ventilation systems, it is desirable to provide access to the filter units on the side of the housing in order to allow access and facilitate the replacement or maintenance. For that reason, one modification of the invention provides an opening for accessing the filter units on the side of the housing, which opening can also be closed. When provided with support legs, the device according to the invention with the cylindrical housing is suitable to be set up as a freestanding unit in factory buildings, workshops and other production areas. Of course, the device can also be used while positioned horizontally or at a slant, for example in air conditioning and ventilation systems for buildings, ships or aircraft.
To simplify the design and operation of the device and at the same time ensure an optimum air-cleaning effect in all filter units, all filter units can be connected to a joint control arrangement. The measures according to another embodiment have a positive effect on the air cleaning because they result in an even load for all filter units, thus achieving on the one hand the best possible cleaning effect and, on the other hand, an extension of the service life for all filter units. By designing the air intake on the housing delimited by an edge surface curved toward the outside in an arc toward the housing outside wall, the air can be suctioned in without eddies from the space surrounding the housing, which considerably improves the effect of the device. A longer service life and longer maintenance intervals for the filter units as well as a secure cleaning effect of the device can be provided by incorporating pre-filtering of the air before it enters the filter units. As a result, larger pollutant particles are filtered out of the airflow before it reaches the filter units. A metal filter can be provided as intake filter, which is installed on the housing such that it can be removed easily and is easy to clean. The filter can be cleaned independent of the maintenance cycles of the filter units. An ozone filter can be provided for removing ozone that develops during the electrostatic air cleaning from the airflow leaving the filter units. The effectiveness of the afterfilter and its easy maintenance in particular are of particular importance for this.
In another advantageous embodiment of the device according to the invention, the cleaned airflow leaving the housing can be equalized. A retaining space can be provided between the outlet for the filter units and the afterfilter. This results in not only a pressure equalization over the complete outlet cross section, but also offer space for one or more fans for moving the air through the filter units. Sound dampening material can be provided to increase the commercial acceptance of the device by reducing its noise emission. A diffuser can be provided to evenly distribute the cleaned airflow leaving the housing.
In one advantageous arrangement, the electrostatic filter units are arranged in parallel with the corresponding pipes. In another advantageous modification, the filter units are installed in the housing and, simultaneously, ensure that the airflow entering the housing flows completely through the filter units and is cleaned. An even more reliable mounting of the filter units in the housing is achieved through the installation of additional support walls, the openings or installation openings of which are aligned axis-parallel and which hold and support the filter units at several locations.
In other arrangements, the housing can be designed as hollow-cylindrical column or as column with a polygonal cross section, for example a rectangular or square cross section.
The present invention can be used in existing air conditioning or ventilation systems.
The device according to the invention has a number of advantages. Combining individual filter units to form at least one assembly that is adapted to the inside of the housing and can be inserted into or removed from the housing facilitates the handling of a device of this type. The user friendliness achieved in this way is important, particularly since the users of such cleaning devices frequently have little or no special knowledge of the equipment.
The device according to the invention has the following advantages:
Designing the device with several parallel filter units permits the cleaning of large flows or air, so that the device is particularly suitable for use in large spaces, such as factory buildings, shops and manufacturing plants for the industry. The housing for the device can be realized in different ways, so that the device can be adapted to various spatial operating conditions. Thus, the device is also well suited to be integrated into existing or newly installed air ducts in the ventilation systems or air-conditioning systems of buildings, ships or aircraft. The filter units used effect a thorough cleaning of the air. In the process, even very small pollutant particles and suspended particles are removed from the air and deposited in the electrostatic filter units. This is achieved in particular with the tube-shaped design of the preferably used filter units. Another advantage of the invention is that the air is guided essentially in a straight line inside the housing and the filter units. Air turbulence and obstacles restricting the flow are therefore mostly eliminated. As a result of the low flow resistance inside the device, only a relatively low fan capacity is required, which reduces the energy requirement and the noise emission of the device, thus making it more acceptable to the user. Yet, the device is cost-effective, requires low maintenance and is versatile and flexible with respect to use.